One of the greatest threats we face as a species is the potential that earth could get hit
by an asteroid or comet.
Not only do we have plenty of evidence that mass extinctions in the past have been caused
by these kinds of impacts, we’ve also been faced with more recent smaller, but still
frightening, events like the Chelyabinsk meteorite fall or the Tunguska event that serve as reminders
that we are still very much under the gun in this star system and it’s only a matter
of time before something bigger comes our way.
But, asteroid impacts are avoidable even with current human technology so long as we can
see them coming ahead of time.
In fact, we have a whole host of options for deflecting something like this before it’s
too late.
They key to all of this of course is our ability to detect dangerous asteroids long before
they hit in order to give us enough time to deflect them.
We already do this to a degree, and our detection abilities improve each year, and in fact many
potentially dangerous objects are already under active surveillance.
A good development for sure but so far, overall we’ve just been lucky.
We haven’t been seriously hit during our time on this planet, and we do not yet see
any immediate threats that would send us into panic mode.
But it could happen at any time and we are overdue.
The good news is that as time goes on, and we technologically advance, doing something
about a potential impactor gets easier and easier.
And some day it probably won’t be a problem at all.
But we still need to get to that day.
But say we did detect a threat in the near term.
How would we mitigate the threat?
There are several ways.
The first is very simple; nuclear weaponry.
We tend to think of nukes as bad things, weapons for a war that no one wants to ever see.
But like many things, nukes can also be a tool and could be used to deflect asteroids.
To accomplish this, you would simply detonate the nuke on or near the asteroid.
For an asteroid that is relatively solid, you don’t necessarily need to completely
destroy it, rather just nudge it in a different direction.
In fact, you would want it to stay as intact as possible, rubble could be a bad thing,
rather you just want vaporized ejecta pushing the asteroid in a slightly different direction
so it misses earth.
Some asteroids, however, are little more than conglomerations of loose rubble.
Here you would want to detonate a series of nukes at more of a distance to nudge the asteroid
without turning it into a hazardous cloud of rock still on an earth intercept course.
Other possibilities include detonating a subsurface nuke inside the asteroid to nudge it, or building
a cradle containing several nukes around the asteroid and detonating them that way.
But the nuclear option isn’t the only option, also possible with current technology is a
simple impactor.
Any object sufficiently large, say another asteroid, or an impactor sent from earth could
knock an asteroid off course enough to have it miss earth, say we positioned a mass driver
to fire materials, or moon rocks, at the object.
We already have some experience with this method, the Deep Impact mission sent a projectile
to impact the comet Tempel 1 in 2005.
While this was designed to blast a crater in the comet to study its interior rather
than to actually perturb it, it was a success and demonstrated that objects in space can
be targeted and struck.
Future missions promise to expand on this by the European Space Agency to study and
even attempt to deflect an asteroid.
More, ESA has determined that it might be possible to deflect the asteroid Apophis,
one of the more spooky near earth asteroids, with as little as a one ton impactor.
But there are other options.
If you have ample time, you might also deflect an asteroid using gravity.
The main advantage to this method is that you don’t create any debris and you don’t
have to worry about how fast the asteroid is spinning, you’re simply using a massive
object’s gravity and propulsion to very slowly pull an asteroid into a different orbit.
Disadvantages are that you would need a seriously large object to have enough of an effect,
and costs are also higher for this approach, and it takes time, at least several years
to decades for a massive spacecraft with an ion drive to tug the asteroid in a different
direction, or even mount a conventional rocket engine on the asteroid and push it that way.
An alternative take to this is to just send an ion drive alone to point at the asteroid
and nudge it with the exhaust, much like spraying a garden hose to move dirt of a patio.
The advantage here is that you don’t need a huge amount of mass to accomplish your goal.
Another method would be to concentrate solar energy on the surface causing material to
evaporate and push the comet or asteroid in a different direction, but this suffers from
the need of some seriously large lenses, basically megastructure lenses.
Other more novel options include wrapping the asteroid in a reflective material, or
painting it, essentially turning it into a makeshift solar sail, or aerobraking the object
by putting material into its path and changing its course.
One simple way would be to change the balance of the asteroid by moving its center of mass
through a tether and ballast.
You might even be able to accomplish this by constructing such a rig from material originating
from the asteroid itself.
One final proposition would be to use a laser array at earth to move the asteroid by vaporizing
surface material to nudge it without actually having to visit the object at all.
This plan is known as DE-STAR, put forth by Philip Lubin and a group at the University
of California at Santa Barbara, link to their website below, that proposes an extremely
powerful multi-use modular laser array that not only could deflect an asteroid, but completely
vaporize it.
Such a system would have more uses than just deflection however, it could also be used
to clear orbital debris around earth, push solar sails to very high speeds opening the
way for interstellar travel, and shortening times for a trip to Mars to as little as three
days.
Also, such a system would be of immense use in asteroid mining, as it would allow interested
parties to prospect an asteroid before even travelling to it.
By vaporizing materials from the asteroid’s surface, the composition could be determined
from earth and then it could be decided whether something is worth mining or not.
Further, asteroids could be manipulated and moved around the solar system with the laser
for easier mining or other projects such as beaming energy around to colonies.
Perhaps most interestingly however, is the potential for very long distance laser communications.
And this aspect holds potentially major implications for SETI.
At the energies required for this system to be able to deflect asteroids, the energies
involved here are on level with a space shuttle solid rocket booster, it would be extremely
bright, in fact for most of the exoplanets we know of so far it would appear as one of
the brightest objects in their sky at the frequency of the laser.
Given enough time for the light to propagate, this might even be visible on intergalactic
scales.
Given the utility of such an array, aliens probably need to move asteroids too, planetary
defense systems like DE-STAR may be among the most common things alien civilizations
build and count as a very visible potential technosignature for future SETI searches.
And, in the end, planetary defense is planetary defense.
Most of the things we’d defend against would be natural objects heading our way, but if
anyone ever decided to send a hostile von Neumann probe or the like towards us, we would
have two lines of defense.
Space nukes and giant vaporizing space lasers.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently worried about alien
space lasers.
What if we find one, in one sense it would be a detection of an alien civilization, but
in another sense it would be a cat-like fascination with the galactic equivalent of a laser pointer.
I can hear the aliens snickering at us already and be sure to check out my books at your
favorite online book retailer and subscribe to my channel for regular, in-depth explorations
into the interesting, weird and unknown aspects of this amazing universe in which we live.